The 2010 study by municipal contractor Biffa, which manages Wirral's collection service, and conducted by Biffa data and carbon reduction manager Dr Matthew Chester, assessed the positive and negative effects of landfill methane production and related power generation, emissions from transport and MRF processing, and any displacing offset emissions.

The study was predicated on the basis that waste sent to landfill can produce harmful methane for up to 10 years, and that increasing recycling diverts waste from landfill and so reduces carbon impact.

Using industry-recognised formulas for calculating the CO2 impact of landfill gas, transport emissions, MRF recovery processes and windrow composting, analysts examined data on Wirral's waste and recycling composition, tonnages and street sweepings.

This comprised around 76,000 tonnes of land-filled waste, 31,000 tonnes of dry recyclables, almost 19,000 tonnes of organic recyclables, and 2,370 tonnes of street sweepings.

Translated into a comparison between landfill-only and Wirral's activities, it found the former would have produced 17,588 tonnes of CO2, while Wirral's recycling efforts would have reduced carbon output by 13,370 tonnes, generating an overall CO2 reduction of 30,960 tonnes.

This is equivalent to switching off 1½ million 40w light bulbs, or taking 4,000 4x4 vehicles off the road.

This calculation, argued Biffa's municipal director Roger Edwards, shows that maximising recycling and diversion from landfill actively contributes to cutting carbon outputs.

"When local authorities persuade residents to recycle more, they often do so primarily because they have to hit government-mandated targets," he said. "But we should never forget that the underlying prime reason for recycling has always been for sound environmental reasons, such as reducing dependence on virgin raw materials and cutting CO2.

"The Wirral analysis proves what can be achieved and gives us an excellent analytic model for the future."

Carbon Reduction

Since the start of the contract in 2006, Biffa and Wirral Council have introduced service changes that have made recycling easier for residents, as well as directly contributing to carbon reduction.

These included introducing alternate collections of recyclables and refuse from wheeled bins, launching a green waste service using wheeled bins and increasing related collections from 90,000 to 110,000 households, and introducing recycling services for schools as well as around 5,000 multi-occupancy properties.

Other improvements were siting the green waste tipping facility within the borough, reducing the number of rounds and related mileage, fitting fuel-saving devices to all collection vehicles, and plotting more efficient routing that cut the number of collection vehicles needed by 10 percent.

In just a few years, Wirral Council has more than tripled its recycling and composting rate, rising from 12 percent in 2005/6 to just over 40 percent in 2010/11.

Darrel Moore